The paper analyzes the sources of declining occupational segregation by gender in West Germany after German re-unification. We focus on the impact of massive, regionally imbalanced inflows of East Germans with distinct labor market attitudes and histories facilitating entry in male dominated jobs. Our evidence on the basis of administrative panel data that allows control of unobserved heterogeneity shows that the labor supply shock from a growing share of East Germans in the West German work force significantly reduced male-female-imbalance within occupations, thus reducing occupational segregation. But apart from this direct effect an additional spill-over effect emerges. It appears that West German women have benefitted from the role model of East German women in the sense that they enter male dominated jobs more frequently in local labor markets with a larger employment share of East German women. These results hold if one controls for possibly endogenous location choices of East-West-migrants.